Systems and methods for preventing overheating in refrigeration systems

ABSTRACT

A refrigeration system for cooling an object and preventing system overheating. The system includes an evaporator coil configured to thermally communicate with the object, where the object is cooled by a refrigerant flowing through the evaporator coil. A compressor receives the refrigerant downstream from the evaporator coil and increases a pressure of the refrigerant. A condenser receives the refrigerant downstream from the compressor, where the refrigerant is cooled by flowing through the condenser. An expansion valve receives the refrigerant downstream from the condenser and decreases the pressure of the refrigerant, where the evaporator coil receives the refrigerant downstream from the expansion valve. An bypass coolant valve also receives the refrigerant downstream from the condenser. The compressor also receives the refrigerant downstream from the bypass coolant valve, and the refrigerant received by the compressor from the bypass coolant valve bypasses the evaporator coil to prevent overheating of the compressor.

FIELD

The present disclosure generally relates to systems and methods for preventing overheating in refrigeration systems, and more particularly to systems and methods for preventing overheating in refrigeration systems by incorporating a bypass coolant valve.

BACKGROUND

The following U.S. patents and patent application provide background information and are incorporated by reference in entirety.

U.S. Pat. No. 6,220,047 discloses a method of controlling the operation of the refrigeration system and the cooling of both evaporator coils thereof. The control system provides for directing refrigerant to one or the other of the evaporator coils as is most efficient so as to avoid short cycling or pressure build up. The disclosed invention uses a control strategy that can more accurately maintain a pre-selected temperature differential between the inlet and outlet temperatures of the evaporator coils. The control algorithm utilizes a proportional integral differential control approach that safely permits a much narrower temperature difference so that a greater length of each freeze cylinder evaporator coil can be utilized for efficient heat transfer cooling.

U.S. Pat. No. 8,701,435 discloses a frozen product dispenser characterized by at least two product freeze barrels for receiving product therein and for freezing the product for dispensing, and a refrigeration system for chilling the at least two barrels. The refrigeration system is controllable to selectively operate one or more of the compressors and one or more of the expansion valves in accordance with the cooling requirements of the barrels to provide an improved turndown ratio for improvements in efficiency of operation of the refrigeration system in response to changing cooling load requirements of the product barrels.

U.S. Pat. No. 9,062,902 discloses a method to defrost one barrel of a two barrel FCB dispenser, a refrigeration system which defrosts the one barrel, while neither defrosting nor chilling the other barrel, for either a selected time or until a frozen beverage is drawn from the other barrel, whichever occurs first. The arrangement keeps beverage in the other barrel properly frozen during defrosting of the one barrel.

U.S. Patent Application Publication No. 2008/0149655 discloses a variable capacity refrigeration system for a frozen product dispenser which is controllable in response to cooling load requirements of the dispenser to have a variable cooling capacity that is in accordance with the cooling load demands placed on the refrigeration system by the dispenser. This is accomplished, in part, by providing the refrigeration system with a variable capacity compressor, the output capacity of which is controlled by varying its operating speed in a manner such that refrigerant output from the compressor generally meets the mass flow of refrigerant through expansion valves of the system. The arrangement provides for efficient operation of the frozen product dispenser from an energy standpoint and for a reduction in on/off cycling of the refrigeration system.

SUMMARY

This Summary is provided to introduce a selection of concepts that are further described below in the Detailed Description. This Summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.

One embodiment of the present disclosure generally relates to a refrigeration system for cooling an object and preventing system overheating. The system includes an evaporator coil configured to thermally communicate with the object, where the object is cooled by a refrigerant flowing through the evaporator coil. A compressor receives the refrigerant downstream from the evaporator coil and increases a pressure of the refrigerant. A condenser receives the refrigerant downstream from the compressor, where the refrigerant is cooled by flowing through the condenser. An expansion valve receives the refrigerant downstream from the condenser and decreases the pressure of the refrigerant, where the evaporator coil receives the refrigerant downstream from the expansion valve. A bypass coolant valve also receives the refrigerant downstream from the condenser. The compressor also receives the refrigerant downstream from the bypass coolant valve, and the refrigerant received by the compressor from the bypass coolant valve bypasses the evaporator coil to prevent overheating of the compressor.

Another embodiment generally relates to a method for cooling an object and preventing overheating of a refrigeration system. The method includes positioning an evaporator coil to thermally communicate with the object, where the evaporator coil is configured to cool the object when a refrigerant flows through the evaporator coil. The method includes fluidly connecting a compressor downstream of the evaporator coil, where the compressor is configured to increase a pressure of the refrigerant received from the evaporator coil. The method includes fluidly connecting a condenser downstream of the compressor, where the condenser is configured such that the refrigerant is cooled by flowing therethrough. The method includes fluidly connecting an expansion valve downstream of the condenser, where the expansion valve is configured such that the pressure of the refrigerant decreases when flowing therethrough, and where the evaporator coil receives the refrigerant downstream from the expansion valve. The method includes fluidly connecting an bypass coolant valve to also be downstream of the condenser and to also provide the refrigerant to the compressor, where the refrigerant received by the compressor from the bypass coolant valve bypasses the evaporator coil to prevent overheating of the compressor.

Various other features, objects and advantages of the disclosure will be made apparent from the following description taken together with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is described with reference to the following Figures.

FIG. 1 is a schematic view of an exemplary refrigeration system presently known in the art, particularly a frozen carbonated beverage (FCB) dispenser;

FIGS. 2 and 3 are schematic views of exemplary refrigeration systems according to the present disclosure;

FIG. 4 is a chart depicting the improved performance identified using refrigeration systems according to the present disclosure over systems presently known in the art;

FIG. 5 is a schematic representation of an exemplary control system as may be incorporated within the presently disclosed refrigeration systems.

DETAILED DISCLOSURE

Environmental regulations are requiring a shift away from current refrigerants, such as R404a, to refrigerants with reduced impacts on global warming, such as R448A. However, through research and experimentation, the present inventors have identified problems with using these alternative refrigerants within presently known refrigeration systems. For example, these problems arise within refrigeration systems within frozen carbonated beverage (FCB) machines. Additional information regarding FCB machines and conventional refrigeration systems more generally is provided in U.S. Pat. No. 6,220,047, which is incorporated by reference herein.

Conventional refrigeration systems use one or more automatic expansion valves each providing a constant mass flow to an evaporator coil, irrespective of load condition and working ambient conditions, such as temperature. The present inventors have identified that, consequently, when alternative refrigerant blends that have a high heat of compression (such as R448A or R452, for example) are used in these conventional refrigeration systems, components of the refrigeration system are susceptible to reliability problems and premature failure. This is particularly true of compressors, which typically have a temperature limit of 275° F., for example. In some tests, the present inventors identified a compressor discharge temperature of more than 280° F. (thus exceeding the limit of 275° F.) in ambient temperatures of 105° F., and even 90° F.

The present inventors have identified that, due to the differences in entropy and enthalpy between R448A and R404A (for example), the high internal energy possessed by R448A results in more heat generated being during the compression than compared to R404A. This in turn results in a higher discharge temperature in overall refrigerant system when substituting R448A over conventional R404A refrigerant. Therefore, if the evaporator coil consequently receives a lesser mass flow rate of R448A, this mass will not be capable of removing the heat from the compressor scroll, thereby increasing the discharge temperature of the compressor and leading to failure as discussed above.

FIG. 1 shows a refrigeration system 20 as presently known in the art, which is shown configured to cool a beverage product within an FCB system. The refrigeration system 20 includes a compressor 22, such as a fixed speed scroll type, that delivers the refrigerant (at that point as a hot gas) from via a discharge line 24 to a condenser 26. The condenser 26 then cools the refrigerant in the conventional manner. In certain embodiments, the refrigerant (now a hot liquid) flows out of the condenser 26 via a condenser outlet line 28 to a pair of constant mass flow rate automatic expansion valves (AEVs) 30 and 32. In other embodiments, a receiver 100 (see e.g., FIG. 2, which is not prior art) is positioned between the condenser 26 and the AEVs 30 and 32.

The AEVs 30 and 32 are configured to provide a constant mass flow rate of refrigerant (now as a cold liquid) to the evaporator coils 34 and 38. In particular, the mass flow rates are constant irrespective of load conditions and the ambient operating temperature for the system 20. The evaporator coils 34 and 38 are configured to provide heat transfer to corresponding product freeze barrels 36 and 40 to chill (or in this case, freeze) a beverage product contained therein.

In certain embodiments, the refrigerant (now a cold gas) exits the evaporator coils 34 and 38 and flows to an accumulator 114 (FIG. 2) before flowing through a suction line 42 back to the compressor 22. In other embodiments, such as the prior art shown in FIG. 1, the refrigerant may instead flow directly from the evaporator coils 34 and 38 through the suction line 42 to the compressor 22.

With continued reference to FIG. 1, the present inventors have identified that the AEVs 30 and 32 do not variably control the mass flow rate of refrigerant to the evaporator coils 34 and 38 to match or otherwise support the requirements of the varying load or ambient operating conditions. Instead, a constant mass flow rate of refrigerant, for example having an evaporating temperature at −12° C., is supplied by the AEVs 30, 32 to the evaporator coil 34 and 38, irrespective of these conditions. As such, the temperature of the refrigerant arriving at the compressor 22 for the system 20 increases at peak load, as does the temperature of the refrigerant discharged from the compressor 22, and thus the compressor 22 itself.

For the systems 20 that use R404A as the refrigerant, the temperature discharged from the compressor 22 would still remain below the maximum temperature limit that would cause damage to the compressor 22 within normal operating ambient temperatures (i.e., 275° F.). However, the present inventors have determined that if an alternative, eco-friendly blend of refrigerant is used within such a conventional system 20, such as R448A, this discharge temperature would exceeds the maximum temperature limit for the compressor 22, even at low ambient temperatures. In short, the refrigeration systems 20 presently known in the art are not equipped to safely and reliably operate using refrigerants having high heat of compression.

FIG. 2 shows a refrigeration system 20 according to the present disclosure. The system 20 shown is similar to that previously shown in the prior art system 20 of FIG. 1. However, the system 20 of FIG. 2 incorporates an additional bypass coolant valve 124, which is fluidly coupled to the receiver 100 via an inlet conduit 126. The bypass coolant valve 12 is also fluidly coupled via an outlet conduit 120 to the accumulator 114, which may be a direct connection, or an indirect connection via the accumulator inlet conduit 112 as shown.

The system 20 of FIG. 2 further includes a sensor 122 that is configured to sense the temperature of a refrigerant flowing through the sensor 122 itself, or through a line (such as the suction line 116) in close proximity to the sensor 122. The bypass coolant valve 124 communicates to the sensor 122 via a line 118. In the embodiment shown, the sensor 122 is a sensing bulb wrapped around the suction line 116 feeding into the compressor 92. It should be recognized that the line 118 may provide a fluid connection between the bypass coolant valve 124 and the sensor 122 (i.e., the bypass coolant valve 124 passively responding to temperature), and/or an electrical connection therebetween (which may be incorporated within a control system 91 that controls the system 20). Additional information regarding the control system 91 is provided below. The bypass coolant valve 124 and sensor 122 may also be packaged together, such as Danfoss Model TUB Thermastatic Expansion Valve, for example.

In the embodiment of FIG. 2, the AEVs 104 and 106 are adjusted, or set to provide a constant mass flow rate of R448A refrigerant, such as would be associated with having an evaporating temperature of −12° C. The refrigerant from the AEVs 104 and 106 flows through the evaporator coils 108 and 110, respectively in the manner previously described. As also previously discussed, each evaporator coil 108 and 110 is wrapped around, and therefore transfers heat with, the freeze barrels 84 and 86, respectively. Likewise, the compressor 92 receives the refrigerant from the suction line 116, and subsequently supplies the refrigerant to the condenser 96 through conduit 94 in the manner previously described.

In contrast to the systems known in the art, the system 20 of FIG. 2 further provides a bypass coolant valve 124 with a corresponding inlet conduit 126 and outlet conduit 120. The bypass coolant valve 124, inlet conduit 126, and outlet conduit 120 provide an alternate pathway for the refrigerant to flow between the condenser 96 (or in this case the receiver 100) and the compressor 92, specifically one that bypasses the evaporator coils 108 and 110. As will become apparent, the refrigerant flowing through the bypass coolant valve 124 will have a different temperature than the refrigerant flowing through the evaporator coils 108 and 110, which impacts the temperature received at the compressor 92 (in this case, by way of the accumulator).

With continued reference to FIG. 2, control of the bypass coolant valve 124, in this embodiment by the control system 91, proceeds as follows. When the sensor 122 detects that the temperature of the refrigerant in the suction line 116 exceeds a predetermined threshold, the bypass coolant valve 124 is opened. For example, the predetermined threshold may correspond to a refrigerant temperature that may harm the compressor 92, such as a value within the range 20° to 80° F., in certain embodiments set at 50° F. This results in a portion of the refrigerant received at the compressor 92 (by way of the accumulator 114) being received directly from the receiver 100, not having been warmed by first proceeding through one of the evaporator coils 108 and 110. In other words, the combined mixture of refrigerant received from the bypass coolant valve 124 and the evaporator coils 108 and 110 has a lower temperature than if the entirely of the refrigerant flowed only through the evaporator coils 108 and 110.

If instead the sensor 122 detects that the refrigerant temperature in the suction line 116 does not exceed the predetermined threshold, the bypass coolant valve 124 may be closed such that all of the refrigerant from the receiver 100 is available to cool the barrels 84 and 86 by flowing through the corresponding evaporator coils 108 and 110, respectively. This in turn increases the performance of the system 20 with respect to cooling times for content within the barrels 84 and 86, for example. It should be recognized that the bypass coolant valve 124 need not be exclusively opened or closed, but may also be positioned in intermediate states depending on the temperature detected by the sensor 122.

FIG. 3 shows an alternate embodiment according to the present disclosure. The system 20 of FIG. 3 is similar to that shown in FIG. 2, but positions a sensor 130 at a different location relative to the compressor 92. In particular, the sensor 130 (which in certain embodiments may otherwise be the same as the sensor 122) is positioned to detect the temperature of the refrigerant exiting the compressor 192 via the conduit 94, rather than in the suction line 116. An exemplary bypass coolant valve 124 and sensor 130, which may also be packaged together, is Danfoss Desuperheating valve, TXI 2. In this case, exemplary temperature thresholds may be within the range of 175° to 230° F., in certain embodiments set at 203° F.

It should be recognized that the sensor 122 and position within FIG. 2 may also be used in conjunction with the sensor 130 and position within FIG. 3, for example to provide redundancy or error checking. Similarly, the precise locations of the sensor 122 and 130 may vary from that shown, such as positioning the sensor 122 upstream of the accumulator 114, closer to the condenser 96 downstream of the compressor 92, and/or the like.

FIG. 4 shows exemplary experimental data collected using a system 20 similar to that shown in FIG. 2, specifically incorporating R448A refrigerant therein. Line “A” depicts the temperature of the refrigerant within the suction line 116 for the compressor 22 in a conventional system (FIG. 1), and Line “B” as discharged from the compressor 92 of the system 20 presently disclosed (FIG. 2). As shown, the system 20 presently disclosed caused a reduction in the temperature of refrigerant versus the compressor 22 in systems known in the art. Moreover, the reduction provided by this use of a bypass coolant valve 124 (also referred to as a desuperheating valve) reduced the discharge temperature enough to maintain a compressor 92 temperature within normal operating limits (i.e., under 275° F. as discussed above) when using R448A refrigerant, which was not the case using systems known in the art (Line “A”). The present inventors identified that reductions in the temperature of the refrigerant were also provided by the system embodiment shown in FIG. 3.

As discussed above, FIG. 5 discloses an exemplary control system 91 for controlling the systems 20 of the present disclosure. Certain aspects are described or depicted as functional and/or logical block components or processing steps, which may be performed by any number of hardware, software, and/or firmware components configured to perform the specified functions. For example, certain embodiments employ integrated circuit components, such as memory elements, digital signal processing elements, logic elements, look-up tables, or the like, configured to carry out a variety of functions under the control of one or more processors or other control devices. The connections between functional and logical block components are merely exemplary, which may be direct or indirect, and may follow alternate pathways

As shown, the control system 91 may include a processing system 310, memory system 330, and input/output (I/O) system X for communicating with other devices, such as input devices 200 (i.e., the sensor 122 or sensor 130) and output devices 400 (i.e., the bypass coolant valve 124). The processing system 310 loads and executes an executable program 332 from the memory system 330, accesses data 334 stored within the memory system 330, and directs the system 20 (FIGS. 2-3) to operate as described above. For example, the pre-determined threshold for the temperature of the coolant at which the bypass coolant valve 124 should open, or close (or be positioned in intermediate states therebetween) may be stored among the data 334 in the memory system 330.

The processing system 310 may be implemented as a single microprocessor or other circuitry, or be distributed across multiple processing devices or sub-systems that cooperate to execute the executable program 332 from the memory system 330. Non-limiting examples of the processing system include general purpose central processing units, applications specific processors, and logic devices.

The memory system 330 may comprise any storage media readable by the processing system 310 and capable of storing the executable program 332 and/or data 334. The memory system 330 may be implemented as a single storage device, or be distributed across multiple storage devices or sub-systems that cooperate to store computer readable instructions, data structures, program modules, or other data. The memory system 330 may include volatile and/or non-volatile systems, and may include removable and/or non-removable media implemented in any method or technology for storage of information. The storage media may include non-transitory and/or transitory storage media, including random access memory, read only memory, magnetic discs, optical discs, flash memory, virtual memory, and non-virtual memory, magnetic storage devices, or any other medium which can be used to store information and be accessed by an instruction execution system, for example.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to make and use the invention. Certain terms have been used for brevity, clarity, and understanding. No unnecessary limitations are to be inferred therefrom beyond the requirement of the prior art because such terms are used for descriptive purposes only and are intended to be broadly construed. The patentable scope of the invention is defined by the claims and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have features or structural elements that do not differ from the literal language of the claims, or if they include equivalent features or structural elements with insubstantial differences from the literal languages of the claims. 

What is claimed is:
 1. A refrigeration system for cooling an object and preventing system overheating, the system comprising: an evaporator coil configured to thermally communicate with the object, wherein the object is cooled by a refrigerant flowing through the evaporator coil; a compressor that receives the refrigerant downstream from the evaporator coil and increases a pressure of the refrigerant; a condenser that receives the refrigerant downstream from the compressor, wherein the refrigerant is cooled by flowing through the condenser; an expansion valve that receives the refrigerant downstream from the condenser and decreases the pressure of the refrigerant, wherein the evaporator coil receives the refrigerant downstream from the expansion valve; and an bypass coolant valve that also receives the refrigerant downstream from the condenser, wherein the compressor also receives the refrigerant downstream from the bypass coolant valve, and wherein the refrigerant received by the compressor from the bypass coolant valve bypasses the evaporator coil to prevent overheating of the compressor.
 2. The refrigerant system according to claim 1, further comprising a sensor configured to sense a characteristic of the refrigerant at least one of entering and exiting the compressor, wherein the bypass coolant valve is adjustable to vary a mass flow rate of the refrigerant therethrough based on the characteristic of the refrigerant sensed by the sensor.
 3. The refrigerant system according to claim 2, wherein the expansion valve is configured to provide a constant mass flow rate therethrough.
 4. The refrigerant system according to claim 2, wherein the characteristic of the refrigerant is a temperature.
 5. The refrigerant system according to claim 4, further comprising a controller in communication with the sensor and the bypass coolant valve, wherein the controller controls the mass flow rate of the refrigerant through the bypass coolant valve based on the temperature of the refrigerant sensed by the sensor.
 6. The refrigerant system according to claim 4, wherein the controller is configured to control the bypass coolant valve such that the refrigerant flows therethrough only when the characteristic of the refrigerant exceeds a predetermined threshold.
 7. The refrigerant system according to claim 2, further comprising an accumulator operationally positioned between the evaporator coil and the compressor, wherein the accumulator is configured to facilitate the refrigerant changing from liquid to gas before entering the compressor.
 8. The refrigerant system according to claim 6, wherein the compressor receives the refrigerant downstream of the accumulator via a suction line, and wherein the sensor is operatively coupled to sense the characteristic of the refrigerant within the suction line.
 9. The refrigerant system according to claim 1, wherein the evaporator coil comprises an evaporator coil.
 10. The refrigerant system according to claim 9, wherein the object is a freeze barrel configured to cool a beverage contained therein.
 11. A method for cooling an object and preventing overheating of a refrigeration system, the method comprising: positioning an evaporator coil to thermally communicate with the object, wherein the evaporator coil is configured to cool the object when a refrigerant flows through the evaporator coil; fluidly connecting a compressor downstream of the evaporator coil, wherein the compressor is configured to increase a pressure of the refrigerant received from the evaporator coil; fluidly connecting a condenser downstream of the compressor, wherein the condenser is configured such that the refrigerant is cooled by flowing therethrough; fluidly connecting an expansion valve downstream of the condenser, wherein the expansion valve is configured such that the pressure of the refrigerant decreases when flowing therethrough, wherein the evaporator coil receives the refrigerant downstream from the expansion valve; and fluidly connecting an bypass coolant valve to also be downstream of the condenser and to also provide the refrigerant to the compressor, wherein the refrigerant received by the compressor from the bypass coolant valve bypasses the evaporator coil to prevent overheating of the compressor.
 12. The method according to claim 11, further comprising sensing with a sensor a characteristic of the refrigerant at least one of entering and exiting the compressor, further comprising varying with the bypass coolant valve a mass flow rate of the refrigerant flowing therethrough based on the characteristic of the refrigerant sensed by the sensor.
 13. The method according to claim 12, wherein the expansion valve is configured to provide a constant mass flow rate of the refrigerant therethrough.
 14. The method according to claim 12, wherein the characteristic of the refrigerant is a temperature.
 15. The method according to claim 14, further comprising coupling a controller in communication with the sensor and the bypass coolant valve, and further comprising controlling with the controller the mass flow rate of the refrigerant through the bypass coolant valve based on the temperature of the refrigerant sensed by the sensor.
 16. The method according to claim 15, wherein the controller is configured to control the bypass coolant valve such that the refrigerant flows therethrough only when the temperature of the refrigerant exceeds a predetermined threshold.
 17. The method according to claim 12, further comprising fluidly connecting an accumulator between the evaporator coil and the compressor, wherein the accumulator is configured to facilitate the refrigerant changing from liquid to gas before entering the compressor.
 18. The method according to claim 17, wherein the compressor receives the refrigerant downstream of the accumulator via a suction line, and wherein the sensor is operatively coupled to sense the characteristic of the refrigerant within the suction line.
 19. The method according to claim 11, wherein the evaporator coil comprises an evaporator coil.
 20. The refrigerant system according to claim 19, wherein the object is a freeze barrel configured to cool a beverage contained therein. 